Prior art flat panel displays include a backplate that includes a matrix structure of rows and columns of electrodes. One such flat panel display is described in U.S. Pat. No. 5,541,473 titled GRID ADDRESSED FIELD EMISSION CATHODE that is incorporated herein by reference as background material. Typically, the backplate is formed by depositing a cathode structure (electron emitting) on a glass plate. The cathode structure includes emitters that generate electrons. The backplate typically has an active area within which the cathode structure is deposited. Typically, the active area does not cover the entire surface of the glass plate, leaving a thin strip that extends around the glass plate. Electrically conductive traces extend through the thin strip to allow for connectivity to the active area.
Prior art flat panel displays include a thin glass faceplate having one or more layers of phosphor deposited over the interior surface thereof. The faceplate is typically separated from the backplate by about 1 to 2 millimeters. The faceplate includes an active area within which the layer (or layers) of phosphor is deposited. The faceplate is attached to the backplate using a glass seal that extends around the active areas of the faceplate and the backplate.
Sub-pixel regions on the faceplate of a flat panel display are typically separated by an opaque mesh-like structure commonly referred to as a matrix or "black matrix." By separating sub-pixel regions, the black matrix prevents electrons directed at one sub-pixel from overlapping another sub-pixel. In so doing, a conventional black matrix helps maintain color purity in a flat panel display. Polyimide material is commonly used to form the black matrix. In addition, if the black matrix is three dimensional (i.e. it extends above the level of the light emitting phosphors), then the black matrix can prevent some of the electrons back scattered from the phosphors of one sub-pixel from impinging on another, thereby improving color purity.
A support structure extends between the faceplate and the backplate. This support structure overlies the black matrix and assures uniform spacing between the faceplate and the backplate. The support structure is typically formed of ceramic material. The support structure may be walls, pins, or any of a number of other shapes.
A focusing structure that is formed over the active area of the backplate directs electron emission from the cathode. More particularly, the focusing structure is formed within the active area of the cathode for directing emissions from emitters. The focusing structure is commonly formed using Polyimide.
The faceplate of a field emission cathode ray tube requires a conductive anode electrode to carry the current used to illuminate the display. Conventional internal structures within the flat panel display include a support structure. Over time, repeated electron bombardment causes the electrical characteristics of the support structure to vary over time. More particularly, the resistance of the support structure changes over time, resulting in spatially nonuniform resistivity. This deleteriously effects the visible image produced. More particularly, spatially nonuniform resistivity causes the deflection of an electron beam either towards or away from the support structure. This produces regions within the visible display that are not properly illuminated. When walls are used as support structures, the deflection of electrons causes visible lines that extend across the visible display. Also, spatially nonuniform resistivity can result in arcing.
Thus, a need exists for a flat panel display that does not produce regions of the visible display that are not properly illuminated as the electrical characteristics of internal components degrade over time. More particularly, a need exists for internal components that do not have varying resistivity over time and that do not produce spatially nonuniform resistivity.